A word ending with the Locative -7th-case-affix is invariably compounded with a word ending in a case-affix, when the compound thus formed is used as an appellative and the resulting compound is tat-puruṣa ,
A sanjña is expressed by the complete word, hence it is an invariable (nitya) compound; for we cannot express an appellative by a sentence.
As, अरण्ये तिलकाः 'wild sesamum' yielding no oil; anything which does not answer to one's expectation. So also अरण्ये माषाः, वने किंशुकाः' anything found unexpectedly.' So also वने बिल्वकाः, कूपे पिशाचकाः.
The case-affix is not elided, in this case, in accordance to sútra (VI. 3. 9.) (The 7th case-affix is not elided after words ending in consonants or in short अ when the compound denotes appellative.),